1. Field of the Invention
The present invention relates to a method of packaging optical parts for optical communication, and more particularly, to a method of packaging optical parts for optical communication, wherein a packaging process for optical parts is automated to improve productivity and to obtain price competitiveness and uniformity of quality, and a high frequency heater for locally transferring heat to only a solder preform is used to minimize thermal deformation of areas except a soldering area, thereby achieving highly reliable packaging of the optical parts.
2. Description of the Prior Art
Recently, as the information and communication technology has been developed rapidly, high-speed communication networks are established between local areas and between countries and a great amount of data are transmitted/received at a high rate therebetween. In long-distance communication and local area communication, an optical fiber has a minimum transmission loss so that optical communication using the optical fiber enables a greater amount of data to be transmitted at a high rate.
Up to now, in the optical communication field, studies on transmission of a large amount of signals at a very high rate have been continuously performed. One of techniques for transmitting a large amount of signals at a very high rate is a wavelength division multiplexing (hereinafter, refer to as “WDM”) transmission technique.
Such a WDM optical signal transmission method has a technical feature in that optical signals with different wavelengths are divided or merged and then transmitted at a very high rate. This system has been employed in a field of data exchange and the CATV industry and the range of use thereof becomes gradually wider.
Key optical parts for use in such WDM transmission should have low production costs, superior optical characteristics and high reliability.
A WDM optical filter, which is a kind of optical part performing a WDM function, comprises an optical device, which is constructed of an optical filter attached to a first optical fiber collimator, and a second optical fiber collimator. The WDM optical filter divides or merges optical signals with different wavelengths transmitted to the first optical fiber collimator and then transmits the signals to the second optical fiber collimator.
Further, the WDM optical filter can be manufactured to have high performance and reliability according to collimator aligning and manufacturing techniques, and characteristics of the optical device varies depending on a packaging technique that is a post-process.
Meanwhile, with rapid increase in demands on products to which the optical communication technology is applied and increase in manufacturers thereby, investments and studies for packaging techniques have been continuously made to enhance price competitiveness.
FIG. 1 is a schematic view showing a state where an optical filter part for optical communication is packaged according to the prior art. This optical filter part for the optical communication is a WDM optical filter part disclosed in U.S. Pat. No. 6,167,175.
To package the optical filter part for the optical communication, a filter holder 15 with a filter 14 therein is bonded and fixed by means of epoxy in the center of three communicating tubes that are branched and surrounded by an outer housing 20.
Hereinafter, three communicating tubes are referred to as first, second and third ports 21, 22 and 23, respectively. A first collimator 10 is inserted into and aligned in the first port 21, and then bonded and fixed to the outer housing 20 by means of thermosetting epoxy 16.
Likewise, a second collimator 11 is inserted into and aligned in the second port 22, and a third collimator 12 is inserted into and aligned in the third port 23. Then, the second and third collimators 11 and 12 are bonded and fixed to the outer housing 20 by means of solder 17 applied through holes 24 and 25 formed in the outer housing 20. Thereafter, optical characteristics are inspected, and the packaging process is then completed.
In the conventional packaged WDM described above, when light in which light with a first wavelength λ1 and another light with a second wavelength λ2 are combined is input into a first optical fiber 31, the light with the first wavelength λ1 reflected on the optical filter 14 is transmitted to the second optical fiber 32 through the second collimator 11 and the light with the second wavelength λ2 passing through the optical filter 14 is transmitted to the third optical fiber 33 through the third collimator 12.
Therefore, the WDM divides such light including light components with two different wavelengths.
The conventional WDM has a disadvantage in that the packaging size increases upon packaging thereof.
Further, since the solder is injected through the holes formed in the outer housing to fix the collimators to the outer housing, the injection of the solder through the holes causes thermal deformation of the entire part due to a long heating time, thereby lowering the optical characteristics.
More specifically, if the heating time is prolonged, heat resulting from a high temperature of 220 to 250° C. produced during a soldering process is transferred to the entire part. Accordingly, thermal deformation is generated depending on a coefficient of thermal expansion. Upon cooling after completion of the soldering process, the heat deformation caused by the high temperature is contracted, so that an optimum aligning state of WDM is changed.
In addition, in case the collimator is fixed to the outer housing by applying the epoxy, it is weak in the fixing strength and vulnerable to thermal deformation. Thus, there is a disadvantage of the deterioration of reliability.
FIG. 2 is a view showing a structure of another optical filter part for optical communication according to the prior art. First and second optical fibers 61 and 62 are fixed by a first capillary 51 and then aligned with a first green lens 52 with a filter 53 fixed in a leading end thereof.
Thereafter, a second green lens 54 is aligned with a second capillary 55 to which a third optical fiber 63 is fixed, and the second green lens 54 are aligned with the filter 53. Then, the respective unit devices are finally bonded and fixed to one another by using epoxy.
In such an optical filter part for optical communication, when light with a first wavelength λ1 is input into the first optical fiber 61 and light with a second wavelength λ2 is input into the second optical fiber 62, the light is merged at the filter 53 through the first green lens 52 and then the merged light is transmitted to the third optical fiber 63 through the second green lens 54.
In case of packaging such an optical filter part for optical communication, since the filter and the green lens are bonded directly to each other by means of epoxy, there is a disadvantage in that the reliability becomes lowered depending on temperature.
Since the thermosetting epoxy for use in fixing a single core collimator to an outer housing is cured by means of heating in a chamber, there is another disadvantage in that the optical part must be remounted on a piece of automation equipment to align the optical filter with the single core collimator as a post-process after the curing process.
Therefore, when the manufacture of the optical filter part is automated, it is impossible to continuously carry out operations, and a semi-automation process requiring workers must be performed. Further, the measurement of optical loss is indispensable for finding an optimum aligning position when the optical part is packaged. To this end, the process of cutting, cleaning and connecting optical fibers and other complicated processes are required.
Consequently, since workers should be involved upon construction of the semi-automation process, this causes a problem in that production costs of parts are increased.